The Artemis Project
Europa, Jupiter's moon. Deep beneath the crust, the oceans are teeming with alien sea life. Shellfish, plants, corals, arthropods, even strange fish and larger sea creatures populate a wide-ranging interconnected web of hidden seas. Volcanism is rampant, warming the mineral-rich waters and creating excellent conditions for energy-harvesting.
The largest cavern close to the surface is known as The Pocket. This is where the initial teams of Stabilizers built their first outposts, with the intent to establish long-term communities capable of surviving indefinitely. Aqua-farming is well established; food and other sundries are efficiently gathered. The Pocket has many deposits of minerals and crystals that can be mined and processed to create strong and versatile construction materials locally.
Colonists arrive at the Doorstep at regular intervals when the Threshold is opened. The arrivals are of four general types: Pioneers (who are tasked with exploring the changing surface of the moon and the labyrinth of seas beneath), Engineers (who develop and operate the machinery and structures needed to run the colonies), Marines (who defend the colonies from hostile sea life, unwanted intruders, and other colonies), and Stewards (overseers responsible for strategy and negotiation).